The present invention relates to a method for enhancing the collection of stool samples which are used for the detection of gastrointestinal cancer.
Common screening tests for gastrointestinal cancers involve obtaining a sample of stool and exposing the sample to one or more reagents specially selected to react with a targeted chemical marker associated with gastrointestinal cancer suspected of being in the sample. If the targeted chemical marker is indeed present in the stool sample, a recognizable result is produced by the screening test. Among the many available chemical markers which are the targets of presently used stool screening tests are hemoglobin and other blood-related proteins, collectively referred to as fecal occult blood (FOB).
Stool is formed in the large intestine. Chyme, the digested but unabsorbed food residue, passes from the small intestine into the large intestine where most of the water present in the thyme is absorbed, usually leaving a small amount of fluid to be excreted in the usually semi-solid stool. Most of the water absorption in the large intestine occurs in the proximal half of the colon, known as the absorbing colon, while the distal colon, also known as the storage colon, functions primarily for storage prior to excretion.
Stool residing in the storage colon, and upon excretion, is normally about three-fourths water and one-fourth solid matter. The solid matter is composed of bacteria, fat, inorganic matter, enzymes and other proteins, and undigested roughage of food among other components. During times of constipation, the level of water in stool is even less because of the longer residence time of the stool in the absorbing colon.
There are a number of techniques commonly used today in the collection of stool samples. The most common technique involves using a small paddle to fish a sample of excreted stool out of the toilet bowl. The sample is then wipe on a test card for further processing. U.S. Pat. No. 3,996,006 to Pagano discloses a device known as HEMOCCULT which utilizes such a technique to test for occult gastrointestinal bleeding by testing for FOB.
Another technique for collecting stool samples involves directly wiping the anal area following defecation with a pliant test wipe known as HEMAWIPE. A number of prior patents disclose the use of such a technique including U.S. Pat. Nos. 4,808,379, 4,804,518, 4,559,949, 4,420,353, 4,367,750, 4,273,741, and 4,259,964. HEMAWIPE also tests for occult gastrointestinal bleeding by testing for FOB.
In other tests, the patient is asked to defecate directly into the collection container. In some tests, the stool sample is tested as collected. In other tests, the stool is liquified prior to testing.
In all of these tests, the stool sample collected is defecated in the normal course of a patient's normal bowel routine. Even so, it is widely recognized that most existing tests for chemical markers such as FOB are subject to a substantial number of false negatives and false positives. The resulting errors can severely hamper diagnoses and are potentially deleterious to the patient's well being.